synthetic surface and spm specific features

tests/node_tests/sem_simulation.py

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+import numpy as np
+import pytest
+from tests.node_tests._shared import make_field
+
+
+def test_output_shape():
+    from backend.nodes.sem_simulation import SEMSimulation
+
+    node = SEMSimulation()
+    field = make_field(shape=(48, 64))
+
+    for method in ("integration", "monte_carlo"):
+        result, = node.process(field, method, sigma=3.0, n_samples=20)
+        assert result.data.shape == (48, 64)
+
+
+def test_flat_surface_zero():
+    """Flat topography (all zeros) should produce all-zero or near-zero SEM signal."""
+    from backend.nodes.sem_simulation import SEMSimulation
+
+    node = SEMSimulation()
+    field = make_field(data=np.zeros((32, 32)))
+
+    for method in ("integration", "monte_carlo"):
+        result, = node.process(field, method, sigma=3.0, n_samples=20)
+        assert np.allclose(result.data, 0.0, atol=1e-10)
+
+
+def test_integration_method():
+    from backend.nodes.sem_simulation import SEMSimulation
+
+    node = SEMSimulation()
+    field = make_field()
+
+    result, = node.process(field, "integration", sigma=3.0, n_samples=20)
+    assert np.all(np.isfinite(result.data))
+
+
+def test_monte_carlo_method():
+    from backend.nodes.sem_simulation import SEMSimulation
+
+    node = SEMSimulation()
+    field = make_field()
+
+    result, = node.process(field, "monte_carlo", sigma=3.0, n_samples=20)
+    assert np.all(np.isfinite(result.data))